Koki Otake

Tooth/skeletal dysplasia, such as hypophosphatasia (HPP), has been extensively studied. However, there are few definitive treatments for these diseases owing to the lack of an in vitro disease model. Cells differentiated from patient-derived induced pluripotent stem cells (iPSCs) demonstrate a pathological phenotype. This study aimed to establish a method for fabricating hard tissue-forming cells derived from human iPSCs (hiPSCs) for the pathological analysis of tooth/skeletal dysplasia. Healthy (HLTH) adult-derived hiPSCs were cultured in a hard tissue induction medium (HM) with or without retinoic acid (RA) under 3D culture conditions, and mineralization and expression of dentinogenesis- and osteogenesis-related markers in 3D hiPSC constructs were evaluated. hiPSCs derived from patients with hypophosphatasia were also cultured in HM with RA. HLTH-derived hiPSCs formed mineralized 3D constructs and showed increased expression of dentinogenesis- and osteogenesis-related markers; addition of RA promoted the expression of these markers in hiPSC constructs. HPP-derived hiPSC constructs showed lower mineralization and expression of dentinogenesis- and osteogenesis-related markers than HLTH-derived hiPSCs, indicating an impaired ability to differentiate into odontoblasts and osteoblasts. This method for fabricating 3D hiPSC constructs allows for simultaneous assessment of dentinogenesis and osteogenesis, with HPP-derived hiPSC constructs recapitulating pathological phenotypes.

Zirconia restorations are becoming increasingly common. However, zirconia reduces the polymerization of dual-cured resin cement owing to light attenuation, resulting in residual resin monomers. This study investigated the effects of dual-cured resin cement, with incomplete polymerization owing to attenuated light through zirconia, on the inflammatory response in vitro. The dual-cured resin cement (SA Luting Multi, Kuraray) was light-irradiated through zirconia with three thickness diameters (1.0, 1.5, and 2.0 mm). The light transmittance and the degree of conversion (DC) of the resin cement significantly decreased with increasing zirconia thickness. The dual-cured resin cement in 1.5 mm and 2.0 mm zirconia and no-irradiation groups showed significantly higher amounts of hydroxyethylmethacrylate and triethyleneglycol dimethacrylate elution and upregulated gene expression of proinflammatory cytokines IL-1β and IL-6 from human gingival fibroblasts (hGFs) and TNFα from human monocytic cells, compared with that of the 0 mm group. Dual-cured resin cement with lower DC enhanced intracellular reactive oxygen species (ROS) levels and activated mitogen-activated protein (MAP) kinases in hGFs and monocytic cells. This study suggests that dual-cured resin cement with incomplete polymerization induces inflammatory responses in hGFs and monocytic cells by intracellular ROS generation and MAP kinase activation.